Do I really need a 4 bank smart charger or will a single charger eventually get them all? What is the benifit to the 4 bank? My poor alternator works very hard after a few hours of stereo play. I am barely around 11.5-12 volts running when the batteries are low, but it eventually gets back to 13.5 after about 2-3 hours of running. Should I consider an upgrade?

If all your blue tops are wired together they would be considered 1 bank. In this case you don't really need a multi bank charger. More important is the output current. For your Optimas I would opt for a 40amp model. I have had great results with the Truecharge 40. It is a multibank charger but you can use it to charge a single bank and still get full output. It also has a setting specifically for gel batteries. They are a little pricey but worth every penny.

Like Scott said, multiple batteries connected together create a "bank". If you have isolated batteries, such as a starting and stereo bank, and you want to charge them both without using a battery switch to connect them together, then you need multiple bank charger.

As for the output of the battery charger it will all depend on how quickly you want to recharge. If you have the time, slower is better.

The four optimas will probably combine into around 340 amp-hours. IF they were completely dead, and you wanted to charge them back up in a single night (so you can go back out on Sunday morning), then you would need to get 340 am-hours in 12 hours, which would require a ~28 amp charger.

If you have all week to charge the batteries back up you will be much better off to get a charger that is 10 to 20 amps instead.

More important than the amps of the charger is that it be a "multi-stage" inteligent charger. The old fashion dumb chargers taper their charge off significantly so even if they are rated at 30 amps they won't deliver it into anything other than a compleltey dead battery. This will dramatically increase charge time.

The inteligent multi-stage chargers charge faster and treat the batteries much better.

I have a five battery bank in my boat and I have struggled to find a charger that can bring them back to charge in 12 hours as well as maintain the batteries.

I bought this 30 amp version from West Marine, and this is the best charger I have ever had. You can select the battery type, temperature and amps. It has a nice internal fan and it regulates the charge based on the needs of the "bank". It is the only one I have found that doesn't overheat during operation. I place my charger on a different battery each time I charge....not sure why, just thought it would be a good idea. This charger is worth the investment.